Background: Low literacy is associated with health disparities in access to health information, understanding of illness / treatment, health status, understanding and use of preventive services, and hospitalizations. Better understanding of patients' health literacy would allow for targeted interventions to reduce identified disparities. However, due to assessment burden, scoring imprecision, and inadequate English and Spanish language equivalence, available health literacy measures are not optimal for use in clinical practice or research. Aims: The aims of this application are 1) to develop English and Spanish language item banks for measuring reading-related health literacy skills; 2) to evaluate the feasibility, validity and acceptability of computer-based methods for comprehensive assessment of health literacy; 3) to develop and pilot computerized adaptive testing (CAT) of health literacy in clinical settings; and 4) to use a theory-driven framework to evaluate the associations between health literacy, patient characteristics, enabling resources, needs, health behaviors related to prevention of cardiovascular disease and cancer, and health status. Methods: State-of-the-science analytical methods will be used to develop sets of health literacy questions ("item banks") to support brief, targeted assessment using CAT. A validated bilingual multimedia "Talking Touchscreen" will be adapted to administer CAT to measure health literacy in English and Spanish primary care patients. A cross-sectional study will use this tool to evaluate the associations between patient characteristics, behaviors, outcomes and health literacy. Significance: This project will advance measurement technique through the development of a state-of-the-science computer adaptive tool that will allow precise and rapid measurement of health literacy, enhance ability to distinguish between language and literacy barriers, and increase understanding of associations between health literacy, health behaviors and health outcomes.